Determination of wave-energy direction



March 31,1925 1,532,108

H. c. HAYES DETERMINATION OF WAVE ENERGY DIRECTION Filed June 25, 1919ssheets-she'et 1 IN VEN TOR.

March 31, 1925- I H. C. HAYES DETERMINATION OF WAVE ENERGY DIRECTION 3Sheets-Sheet 2 Filed June 25 1919 INVENTOR. M01774? March-31, 192s-1,532,108

H. C. HAYES DETERMINATION OF WAVE ENERGY DIRECTION IN V EN TOR.

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circumference of a circle.

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HARVEY C. HAYES, OF NEW LONDON, CONNECTICUT, ASSIGNOR TO SUBMARINE SIG-NAL COMPANY, OF PORTLAND,-MAINE. A CORPORATION OF MAINE.

'DETERMINATION OF WAVE-ENERGY DIRECTION.

Application filed June 25,

termination of wave energy direction and more particularly to thedetermination of the direction of wave energy by means of a plurality ofwave energy receptors disposed in a circle, whereby the determination ofthe direction of wave ener y passing over the circle in any directionmay be determined. The determination of the wave energy direction ispreferably eifected by a detecting device connected with the receptorsby connections so arranged as to bring the received wave energy intophase at the detecting device. The circle of receptors may be turnedwith relation to the direction' of. incident Wave energy to bring theenergy in phase at the detecting device, but preferably the circle ofdetectors is fixed. and the wave energy is brought into phase at thedetecting device by shifting the connections from the detecting devicealong the circle of receptors. The present invention is applicable tothe determination of the. direction of various kinds of wave energy, forexample, radio energy. The invention has been embodied in apparatus fordetermining the direction of submarine sounds and will be explained withparticular reference to such embodiment, although it is understood thatthe invention is not limited to the determination of the direction ofsound energy. I

As embodied in a submarine sound detecting device, the apparatuscomprises a plurality of receptors of sound energy disposed at equalangular distances around the These receptors are usually of themicrophonic type. The impulses from the several receptors are brought tothe listening station which may be at a distance from the circle ofreceptors, through wires which may or may not be bound together in acable. At the listening station the electrical impulses are transformedagain into sound transmitted to the listeners ears through suitablelistening apparatus. The connections from the micro- 1919. Serial N'0.306,686

phones are brought, preferably through transformers, to outputterminals. The telephonic receivers or translating devices whichtransform the electric impulses into sound waves are connected withinput terminals which are connected at will to the difi'erent outputterminals. This is preferably accomplished by disposing the outputtermlnals and input terminals in a circular arrangement ofcontact blocksand brushes so that by moving the brushes over the contact blocks theangular relation of the input terminals to the output terminals andconsequently to the receptors, may be varied at will by the operator.Between the input terminals and the listening device at the ears of theobserver are interposed compensated connections to impose relativelydifferent time lags on the energy waves coming from the several inputterminals to the ears. This may be accomplished by connecting theseveral receivers to the ears by using air paths of properlyproportioned length to bring the air waves into phase at the ear, or theelectrical currents from the input terminals may be led over loadedelectric lines to introduce different time lags and the currents broughttogether at telephonic ear pieces, the loaded lines being soproportioned as to bring the currents into phase.

In the drawings which illustrate the preferred embodiment of theinvention as applied to submarine sound detection, Fig. 1, is aschematic view showing the circle of receptors and the connections tothe detecting device. Fig. 2, is a schematic view showing the receptorsand-connections, and particularly the slip ring connections from thecommutating switch to the several telephonic receivers. Fig. 3, is anelevation, partial in section, of the commutating switch and slip rings.Fig. l'is a cross section along the line IVIV of Fig. 3. Figs. 5 .and 6,are diagrammatic views showing air path connection from the severalreceivers to the Stethoscopes. Fig. 5' showing a stethoscope arrangementfor binaural listening and Fig. 6 showing a stethoscope arrangement forlistening to a maximum, but without binaural. Fig. 7 is a detailed viewshowing a section through one of the receivers for translating theelectrical impulses into sound waves.

. Referring to the illustrated embodimentof the invention referencenumerals 136 inclusive, indicate thirty-six microphonie receptors ofsubmarine sound spaced equally around the circumference of a circle. Inpractice this circle has been made eight feet in diameter and thirty-sixmicrophones have been used, but the dimensions and number of microphonesmay be varied. The microphones may be of any suitable submarine type.The type of microphone with its rubber housing for submarine workdisclosed in my U. S. Letters Patent No. 1,470,733, dated October 16,1923, is well adapted for this purpose. In practice the microphones areusually mounted on a rigid circular frame to hold them in proper spacedrelation.

The circle of microphones may be supported in any one of a number ofpositions as will be understood by those skilled in the art.

()ne lead from each microphone indicated by reference numerals 1, 2,etc., joins a common ground wire G. This wire connects with one terminalof a battery B. The other lead from each of the microphones passesthrough the primary of a transformer, the series of transformers beingindicated by reference numerals.1, 2, etc., there being a transformerfor each microphone. The transformer primaries are connected togetherthrough the conductor E to the other terminal of the battery. Thebattery switch BS is shunted by the condenser SC which absorbs theelectromagnetic energy of the circuit when the switch is opened, therebyprotecting the microphones against packing. The wires from the severalmicrophones to the battery and transformers may be lead through a cableto the listening station which in general is located at a distance fromthe receptors. One terminal of the secondary of each transformerconnects with the common lead F, and the other terminal is connected toone of the segments 1, 2, 3 etc., which are arranged as a series ofstationary blocks, indicated at (Z in the structural View shown in Fig.3. A series of brushes, 6 mounted on a rotatable plate I), are arrangedto move over the series of stationary blocks d. As shown in Fig. 1,there are fourteen of these brushes indicated by reference characters 12 to 14 inclusive. These brushes are connected with translating devices,numberedl, 2 etc. to 14. These translating devices are receivers of thetelephonic type which transform the electric current received by meansof the brushes into sound ing through the receivers 1', 2, etc.,respectively and thence through the common lead 0 to the conductor F.Each transformer secondary whose switch segment is not in contact with abrush is open.

The receivers 1, 2 .etc., are divided into two groups of seven receiverseach. Each group is connected with an air column T. The aircolumns T areconnected with a stethoscope S. connected independently to therespective ear pieces of the stethoscope as shown in Fig. 5 for binaurallistening, or the air columns may be joined in a Y as shown in Fig. 6which branches to the two ear pieces of the stethoscope, in which casethe direction of sound is determined by maximum sound but withoutbinaural.

Referring particularly to Fig. 1, suppose that the direction of thesound is that indicated by the arrow N, the wave front beingperpendicular to this direction. This sound can only reach the listenersears through the fourteen microphones, whose secondary circuits areclosed by the fourteen brushes 1 2 etc. These particular microphones arethose numbered 4, 6, 8, 10, 12, 14, 16 on one side of the circle, and34, 32, 30, 28, 26, 24 and 22 on the other side of the circle. It

is evident, therefore, that for sound pro- -wave front. Also microphonesnumbered 6 and 32 respectively will receive sound impulses in phase, butsomewhat later than the pairs numbered 4 and 34, the actual time lagbeing the time required for the sound to travel the perpendiculardistance between the line joining microphones 4 and 34 and the linejoining microphones 6 and 32. Similarly, the pairs of microphones 8 and30, 10 and 29, 12 and 26, 14 and 24, 16 and 22 each receive the soundimpulses in phase but the response from each pair is delayed somewhatwith respect to the preceding pair. The actual time lag between theimpulses received by any two pairs is obviously the time required forthe sound to travel the perpendicular distance between the straightlines joining the microphones of each pair. The time lag between any twopairs of microphones will be proportional to the difference in thecosines of the angles subtended between the direction N through thecenter of the circle and the radii joining such microphones with thecenter.

The responses from the various pairs of receivers 1 and 14*, 2 and 13, 3and 12 etc.,.\ vill be timed in accordance with the corresponding pairsof microphones, provided the time constants of the various electriccircuits are the same. It is important, as will be shown, that theresponsesfrom the The air columns T may be various receivers shall reachthe listeners ear 1n phase. In the arrangement illustrated, this isaccomplished by making the length of the air path between the receiverand the ear different for different pairs of receivers. Consider theleft hand group of receivers 1 2 to 7 inclusive. If the length of airpath which the sound from receiver l travels over and above, that whichthe sound from receiver 2 has to travel to reach the listeners ears is23/100 of the distance that the sound travels to reach the microphone 6,over and above that traveled to reach the microphone 4-, then theresponses from the receivers 1 and 2 will reach the ear in phase, sincethe ratio of velocity of sound in the air to the velocity of sound inwater is 23 to 100. Alsoif the difference in length of air path betweenreceiver 1 and 'each of the other receivers of this group be similarlydetermined, then the sound from all seven receivers will reach thelisteners ear in phase.

From conditions of symmetry it is evident that the same combination ofair pathdistances will bring the sounds from the other or left handgroup of receivers into phase. Sounds from a direction other than thatindicated by. the arrow N, for example the direction indicated by'arrowN E, will reach the listeners ears out of phase. The sound from thisdirection, N E, can be brought to the listeners ears in phase byrotating the circle of microphonic receivers in a clockwise directionthrough the angle subtended between two directions N, and N E. The soundis, however, preferably brought into phase by leaving the circleofmicrophonic receptors fixed, and rotating the plate D, with the brushes6 in a clockwise direction through the same angle. This latter methodwhich is shown in the illustrations, avoids rotating heavy parts andpermits of easy and rapid manipulation. It also permits the compensatorswitch to be placed at any distance from the microphonic receptors.

It is to be understood that the showing in Figures 1 and 2 is schematiconly and that the dimensions for the various parts are not proportionedas actually constructed. For example, the circle of microphonicreceptors is in practice about eight feet in diameter, while the' switchmay be only about a foot to a foot and a half in diameter.

In practice, the receivers are not attached to the rotating elements ofthe compensator switch as shown in Fig. 1, but make brush contact onfourteen separate slip-rings which in turn are electrically connected tothe brushes 1?, 2 etc., as shown diagrammatically in Fig. 2. Thisarrangement avoids the possibility of twisting and breaking the electricleads.

The structure of the switch is shown in Figures 3 and 4. The switchconsists of an insulating plate D to which is secured an insulatingcylinder Q which carries fourteen slip-rings R. Fixed insulating blocksA carry brushes B which make contact with the slip-rings. Two of thebrushes c are shown, which make a contact with the series of transformerterminal blocks d.

For convenience the series of blocks (Z may be regarded as the outputterminals of the microphone lines and the brushes e as the inputterminals of the leads to the translating device which are thetelephonic receivers 1 2, etc. The plate D and the cylinder Q, can berotated about the fixed tube V being held. centered byan externalbearing 0, and an internal bearing H. This rotation is accomplished by asmall hand-wheel W which is rigidly connected to the cylinder and discthrough the rod U. of the received sound is indicated by means of apointer P moving on an angular calibrated scale K. Contact tensionbetween the brushes e and blocks d, can be adjusted by means of the nutN. Electric connections between the brushes 6 and slip-rings The soundimpulses are brought to the ear through stethoscope leads S, whichconnect with extensions of the collector tube T, Figures 5 and 6. Eitherof two methods may be used in connecting these tubes to the ear,depending whether the maximum or the binaural principle is used by thelistener for determining the direction of the sound source.

If the stethoscope leads are connected to the collectortubes T, throughthe Y connection indicated in Fig. 6, then the sounds from all of thefourteen receivers 1 2,- etc., reach both of the ears. is proceedingfrom the direction N indicated in -Fig. 1, it will reach the ears of thelistener in phase. As a result the impulse from all fourteen receiverswill add and the intensity of the received signal will be relativelyclear and loud. If the compensator switchis rotated either side of thisposition the impulses from the fourteen receivers will reach the earsmore and more out of phase and as a result the impulse from thesereceivers will not add perfectly, but will become weakened andindistinct. The direction of the sound source will be determined by thatposition of the compensator which gives a maximum of intensity of thereceived sound.

If the collecting tube T for the right group of receivers, I to 7inclusive, is connected by a stethoscope lead to the right ear and theleft hand group of receivers, 8 and 14 inclusive, are similarlyconnected to the left ear as shown in Fig. 5, then the impulses Thedirection If the sound lull from a sound coming in the directionindicated by the arrow N will reach both ears in phase, but only theimpulses from seven receivers will reach each ear. The sound will appearto the listener to be located in the plane normal to the line joiningthe two ears. The intensity of the sound will be relatively strong andclear in character, because of the fact that impulses from the severalreceivers connected to each ear are in phase. If now, the compensatorswitch is turned in either direction from this position, the intensityof the sound becomes weaker and less distinct in character. Moreover thesound will appear to the listener to move away from the median plane, toone side or the other depending upon which direction from the cen teredposition the compensator switch has been turned. The sense of directionas determined by the two ears depends largely on the time which elapsesbetween the corre; sponding sound impulses in the two ears. If the rightear receives the sound before the left ear does, then the sound appearsto come from the right. The variation to the right depends upon themagnitude of the interval. Similarly, if the sound reaches the left earfirst, the listener judges the sound to be on his left. This sense ofdirection is termed the binaural, and a device employing this sense issaid to depend upon the binaural principle for operation.

If the sound comes from the direction indicated by the arrow NE, it isevident that the group of receivers connected to the right ear receivethe sound impulses before those connecting with the left ear; and as aresult, the sound impulses reach the right ear somewhat before theyreach the left ear. The sound therefore, appears to the listener to comefrom the right and moreover the sound will be weak and of poor quality,because the impulses from each group of receivers reach the respectiveears out of phase.

If the compensator switch is rotated clockwise, this sound will appearto rotate anti-- clockwise and become louder and more clearly defined.The actual direction will be determined by the position the switchoccupies when the sound appears to the listener to be binaurallycentered and to be at a maximum of intensity. It will be noted that theinstrument, so connected to the ear, 0 erates both on the maximum andthe binaura principle. .In the apparatus as above described thereceivers are employed for transforming the electric impulses from thetwo groups of microphones to sound, and the sounds from the severalreceivers are brought into phase by air columns of predetermineddifference in length.

The process of bringing the sounds from several receivers in phase atthe listeners ears,b introducing proper time lag in the path rom eachseparate receiver 1s called compensation. In the foregoing descriptionthis has been described as accomplished by passing the sound throughtubes of properly determined length. The invention, however, is notlimited to compensation by varying lengths of air columns. Compensationmay be accomplished in other ways.

*As shown in the drawings, the compensator brushes and contact blocksare arranged so that every other microphone of the right hand and lefthand sets has a corresponding brush on the'movable plate. 'The inventionis not limited to such a construction. This construction, however, hasthe advantage that it makes possible the accurate determination ofdirection to within an angle equal to half the angular spacing betweenthe microphones. This is due to the fact that two microphones areconnected in parallel to each receiver when the brushes bridge twoblocks. Under such conditions the adjacent pairs of microphonesconnected to each receiver produce sound which has a phase equal to theresultant of that actuating the two corresponding microphones of eachpair. This resultant sound is identical in phase with that which wouldbe given by a microphone located on the circle half way between the pairin each case.

It is to be noticed that when the compensator switch is turned, doublethe number of microphones are in service while the brushes are bridgingtwo blocks that are in service when each brush touches one block andthat there are never more than two mircrophones connected to any onereceiver.

While it is preferred to arrange the apparatus so that the microphonicreceivers are in two sets of groups symmetrical with respect to thatdiameter of the circle passing through the sound source so that thebinaural principle may be used, the apparatus may be operated on themaximum principle only without so grouping the receivers therebysimplifying the construction somewhat. Moreover, the apparatus may beoperated on the binaural principle by connecting only a singlemicrophone to each ear-piece.

While the preferred invention has been illustrated and described, it isto be understood that it is not limited to its illustrated embodimentbut may be embodied in other structures within the scope of the follow--1 ing claims.

I claim:

1. In apparatus of the character described, the combination of aplurality of receptors of wave energy disposed in a circle, a detectingdevice having a plurality of branch energy transmitting paths, and meansfor connecting the branch paths to the circle of receptors in varyingangular relation to the circle but with fixed angular relation withrespect to each other, the

branch paths -having predetermined time difference of energy traverseequal to the differences in time of arrival at the receptors to whichthey are connected, of wave ener passing in a' certain direction acrossthe circle of receptors, substantially as described.

2. In apparatus of the character described, the combination of aplurality of receptors of wave' energy disposed in a circle and havingoutput terminals disposed in 'a' circle and angularly' spacedcorresponding to the angular spacing of the receptors, and means forcollecting and utilizing the received energy comprising a plurality ofbranch. energy transmitting paths having input terminals disposed in acircle and adapted to connect with the circularly to thereby bring thereceived wave energy into phase, and means for relatively angularlyshiftingthe input and output terminals to bring into phase energypassing across the circle of receptors in any direction, substantiallyas described.

3. In apparatus of the character described, the combination of aplurality of receptors of sound energy dis osed in a circle, an auditorydetecting evice having two ear pieces, and means for bringing thereceived sound into phase at the detecting device comprising connectionsfrom the ear pieces to the receptors located diametrically. opposite onthe circle, said connections being angularly shiftable with I respect tothe circleof'receptors, substantially as described.

4. In apparatus of the character described, the combination' of aplurality of receptors of sound energy disposed in a circle, an auditorydetecting device, and means for collecting and bringing into phase atthedetecting device the received sound energy comprising two sets ofbranching energy transmitting paths adapted to be con nected to two setsof a plurality of receiv'ers each on opposite sides of the circle andhaving time differences of energytravel HARVEY CL HAYES.

